Chris Ellis, assistant professor of political science at Bucknell University in Lewisburg, Pa., said traditionally the debates don't do that much to sway voters one way or another.

"The presidential debates always provide one or two memorable moments: The 'Are you better off now than you were four years ago," or the "You're no Jack Kennedy,'" Ellis said in a statement. "But by the time we get to the debates, unless one of the candidates really outperforms the other, most of the voters have more or less made up their minds."

However, David J. Lanoue of Columbus State University in Georgia and co-author of "The Joint Press Conference: The History, Impact, and Prospects of American Presidential Debates," said outstanding debate performances have made a difference in past years.

"Debates can sometimes provide candidates with a measurable bump that can change the complexion of a close race, at least in the short term," Lanoue said. "Debates likely played a meaningful role in the outcomes of the 1980 and 2000 elections, and may also have helped to shape the results in 1960, 1976 and 2004 -- although the big debate winner in 2004 was Sen. John Kerry, a Democrat, who fell short in November against Republican George W. Bush."

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